Generally, the most important figure of merit in heterojunction tunneling diodes is the peak-to-valley (P/V) current ratio. This ratio needs to be as high as possible. To date, the highest P/V current ratio at room temperature is 144, obtained in an In.sub..52 Al.sub..48 As/In.sub..53 Ga.sub..47 As double quantum well, Esaki tunneling diode. This diode is disclosed in an article entitled "P-N Double Quantum Well Resonant Interband Tunneling Diode With Peak-to-Valley Current Ratio of 144 at Room Temperature", by H.H. Tsai et al., IEEE Electron Device Letters, Vol. 15, No. 9, September 1994. The mechanism for the improved P/V current ratio was proposed by M. Sweeny and J. M. Xu in Applied Physics Letter, 54, 546 (1989) and is disclosed in an abstract entitled "Demonstration of a DQW Resonant Tunneling Diode with a 300K Peak-to-Valley Ratio over 100", Abstracts of the 1992 International Conference on Solid State Devices and Materials, Tsukuba, 1992, pp.711-712.
In the above described double quantum well device the improvement is claimed to be the coincidence of the resonance condition between the quantized states and the interband tunneling condition in Esaki diodes. Although the coincidence of the two conditions should in principle give enhanced peak tunneling current, there are no qualitative estimates in the disclosure about the magnitude of the current. In documented experiments attempting to prove this theory, some important parameters were left out, making the conclusions uncertain.
It would be highly desirable to provide heterojunction tunnel diodes with high P/V current ratios.
Accordingly, it is a purpose of the present invention to provide new and improved heterojunction tunnel diodes with improved P/V current ratios.
It is another purpose of the present invention to provide new and improved heterojunction tunnel diodes with improved P/V current ratios in which the materials utilized substantially enhance the peak current.
It is a further purpose of the present invention to provide new and improved heterojunction tunnel diodes with improved P/V current ratios in which the materials utilized reduce the valley current.